Modern internal combustion engine systems often utilize aftertreatment devices to treat the engine exhaust and reduce exhaust emissions. Commonly used devices include catalytic elements, such as oxidation catalysts, catalyzed particulate filters, and selective catalytic reduction (SCR) systems. Many catalytic elements have catalyst materials which are neutralized, deactivated, or experience reduced effectiveness when exposed to sulfur compounds over time. The deactivation by sulfur over time is an accumulative process, limiting the effective life of the catalytic component, or requiring periodic removal of the sulfur compounds.
Presently known sulfur removal processes require bringing the targeted aftertreatment component up to a very high temperature, typically to a temperature exceeding even particulate filter regeneration temperatures. Typical sulfur removal processes involve temperatures exceeding 650° C., 700° C., or 750° C. Immediate catalyst failures can occur at 900° C., 850° C., 800° C., or lower, due to the catalyst composition, physical structure and materials, required activity level to meet the mission of the catalyst, limiting reaction mechanism in the aftertreatment system at various operating conditions (e.g. mass transfer limited—pore diffusion, bulk diffusion, or surface diffusion, reaction rate limited, etc.). Even at lower temperatures within the designed sulfur removal range, greatly accelerated catalyst and other component aging can occur. Also, where high temperatures are required that would not normally, or only rarely, be experienced during normal operations of the application, presently known desulfurization operations may significantly impact fuel economy, mission performance of the engine, and/or be impractical during operations and require that desulfurization be performed as a service event. Performance of desulfurization is undesirable as this increases costs and causes downtime of the system.
Because the aftertreatment component to be regenerated is typically inline with the entire exhaust system, when the sulfur removal occurs during operation on an application (e.g. for a truck in the field), and even in some situations as a service event, the entire aftertreatment system is heated similarly to the component to be regenerated. If the heating is to occur in isolation for the single aftertreatment component, a removal and service process must occur that takes the application (e.g. a vehicle) offline during the process.
The high temperatures experienced during previously known sulfur removal processes greatly increase the aging of the catalyst and other components of the aftertreatment system. Further, components upstream of the regenerated component may need to be heated to an even greater temperature to accommodate heat losses in the system and ensure the downstream regenerated component achieves the required temperature. The response of the system to aging of components and sulfur removal is generally exponential with temperature. Accordingly, minor control variations in the sulfur removal temperature either greatly extend the sulfur removal process time (low temperature), cause the sulfur removal process to fail (too low of a temperature), greatly increase the aging of catalytic or other aftertreatment components (high temperature), or cause immediate failure in catalytic or other aftertreatment components (too high of a temperature). A poorly controlled temperature during a desulfurization can cause both excessive aging and extended desulfurization time, and as such, further advancements in this area are desirable.